Journal of National Fisheries University

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We investigated the oxygen and acid–base status of the densely lamellated oyster, Ostrea denselamellosa, during air exposure for 24 h. The hemolymph O_2 partial pressure decreased from 68.0 torr (mean value) to 52.1 torr during air exposure for 18 h, and reached 42.1 torr after 24 h. The hemolymph pH decreased from 7.579 to 6.798 at 18 h and to 6.361 at 24 h. The hemolymph CO_2 partial pressure increased from 1.30 torr to 40.9 torr at 24 h during air exposure. The hemolymph bicarbonate concentration increased from 1.36 mM/L to 2.81 mM/L at 24 h. The hemolymph calcium ion concentration increased from 8.2 mM/L to 10.9 mM/L at 24 h. From these results, it was revealed that the densely lamellated oysters caused a progressive hypoxemia by hypoventilation of the gill during air exposure. The densely lamellated oysters were inhibited from releasing CO_2 from the gill by hypoventilation, and respiratory acidosis was caused due to the accumulated CO_2. The densely lamellated oysters exposed to air for a long time developed metabolic acidosis due to anaerobic metabolism partially compensated with mobilized [HCO_3^–] from the shell valve.
PP. 1 - 9
To improve breeding techniques for aquarium freshwater pufferfishes, hormone injection (hCG, 10 IU per g)-induced maturity and insemination of Auriglobus modestus from Thailand were undertaken, and morphological development of eggs and early stage larvae observed. Artificial insemination was performed two to five days after hormone injection. Although no fertilized eggs resulted from artificial insemination utilizing a wet (freshwater) method, an isotonic (sodium lactate ringer solution) method produced 458 fertilized eggs out of 787 eggs (fertilization rate 61.7%) spawned by one female, although only 8 larvae (1.7%) eventually hatched. Eggs were oval [long axis 2.05 ± 0.06 mm, short axis 1.68 ± 0.06 mm (n = 5)], translucent, demersal, and adhesive, and contained a number of small yellow oil globules. Oval eggs are unusual among pufferfishes, although common in the genus Chonerinos, an indication of the genetic closeness of the latter and Auriglobus, but also suggesting ecological similarity. The eggs hatched after 2 days, larvae one day after hatching [4.54 ± 0.34 mm NL (n = 9)] having a large yolk sac. However, the mouth remained unopened, the optic vesicle uncolored, and the pectoral fin membrane undeveloped, except for small knob-like rudiments. Seven days after hatching, larvae [5.22 ± 0.10 mm NL (n = 3)] had lost the yolk sac and acquired rudimentary soft rays in the pectoral, dorsal and anal fins. All larvae died after eight days. DNA barcoding comparisons (COI gene, 652 bp) of several pufferfish genera indicated a close genetic relationship of Auriglobus and Chonerhinos, being nested in the same clade.
Momota Kazuyuki Doi Hiroyuki Hashiguchi Yasuyuki Sakai Harumi Murakami Shoki Obata Hiroshi
PP. 11 - 20
An unusual instance of biting behavior by the pufferfish Arothron meleagris, possibly related to spawning behavior was observed during low tide of new moon spring tide while scuba-diving off the Maldives Islands. Multiple males were following, biting and clinging persistently to a female. Subsequent internet searches revealed that similar biting behavior was common among several congeners, possibly being a characteristic spawning-related behavior of the genus.
Doi Hiroyuki Maei Kaori Yoshitake Takafumi Momota Kazuyuki Sakai Harumi
PP. 21 - 25